1. Field of the Invention
The invention relates generally to targeted gene delivery, and more particularly to the use of a recombinant virus comprising a fusogenic molecule and a distinct affinity molecule.
2. Description of the Related Art
The delivery of functional genes and other polynucleotides into particular target cells can be used in a variety of contexts. For example, gene therapy can be used to prevent or treat disease. A particularly desirable gene delivery protocol would be able to precisely deliver a gene of interest to specific cells or organs in vivo. Certain viruses are naturally suited for gene delivery, and significant effort has been focused on engineering viral vectors as gene transfer vehicles. Among these viruses, oncoretroviral and lentiviral vectors exhibit promising features because they have the ability to produce stable transduction, maintain long-term transgene expression and, for lentiviruses, enable transduction of non-dividing cells. Targeting such viruses to particular cell types has proved to be challenging.
Many attempts have been made to develop targetable transduction systems using retroviral and lentiviral vectors (see, for example, D. Lavillette, S. J. Russell, F. L. Cosset, Curr. Opin. Biotech. 12, 461 (2001), V. Sandrin, S. J. Russell, F. L. Cosset, Curr. Top. Microbio. Immunol. 281, 137 (2003)). Significant effort has been devoted to altering the envelope glycoprotein (env), the protein that is responsible for binding the virus to cell surface receptors and for mediating entry. The plasticity of the surface domain of env allows insertion of ligands, peptides and single-chain antibodies, which can direct the vectors to specific cell types (N. V. Somia, M. Zoppe, I. M. Verma, Proc. Natl. Acad. Sci. USA 92, 7570 (1995)). However, this manipulation adversely affects the fusion domain of env, resulting in low viral titers. The unknown and delicate coupling mechanisms of binding and fusion make it extremely difficult to reconstitute fusion function once the surface domain of the same molecule has been altered.
Another approach involves complex env with a ligand protein or antibody to form a bridge to attach the virus to specific cells (e.g., K. Morizono, G. Bristol, Y. M. Xie, S. K. P. Kung, I. S. Y. Chen, J. Virol. 75, 8016 (2001). The challenge to this approach is that env, once complexed with the one end of the bridge molecule, fuses inefficiently. Since no practical strategies are available for targeted in vivo gene delivery, current gene therapy clinical trails are generally based on in vitro transduction of purified cells followed by infusion of the modified cells into the patient. This in vitro approach is an expensive procedure with significant safety challenges.